The intent of the project is to investigate the immunogenetic properties of alloantigen systems in the mouse. The main thrust will be the recombinational analysis of the H-2 gene complex. Congenic strains will be produced bearing new recombinant H-2 haplotypes. The new recombinants will be serologically characterized. The genetic regulation of the alloimmune response will be investigated. The available congenic lines as well as strains with the more recently obtained H-2 recombinants will be used to produce more discriminating serological reagents to be used in the genetic analysis of H-2.